Treatment of hydrocarbon gases



INVENTOR HAROLD l( ATWELL BY )o Q EL s ZZ- H. V. ATWELL TREATMENT 0F HYDRoc'ARBoN GASES Original Filed Oct. 31, 1934 sept, 17 1 940.

ATTORNEY Patented sepa 11, 1940 ,PATENT OFFICE' TREATMENT F HYDBOCABBON GASES mmm v. Atweu, wliue mlm, N. Y., um to Process Management Company, Inc., New York, N. Y., a corporation of Delaware original application october a1, 1934, sei-uu Nn.

Divided and this application October 8, 1937, Serial No. 167,908

My invention relates to the treatment of hydrocarbon gases and more particularly to the conversion of such gases to low-boiling normally liquid hydrocarbons suitable for use as motor fuel.

It is known that hydrocarbongases containing oleflnic constituents such for example as ethylene, propylene and butylene can be effectively polymerized by subjecting them to elevated temperature under high pressure, with resultant formation of low boiling normally liquid hydrocarbons which are high in anti-knock value and can be used as motor fuel. Where, however, as in the usual instance, the source of the hydrocarbon gases comprises uncondensible gases produced in the cracking of hydrocarbon oil, such polymerization under the influence of heat and pressure tends to produce a product containing a relatively large portion of light ends.

It is Aalso known that polymerization of such gases can be promoted even under lower temperature and pressure conditions by means of certain catalysts, prepared by combining a metallic halide with a polar compound, such as sodium chloride,

and a'catalyst which has been found especially suitable for this purpose comprises a sodium aluminum chloride (NaClAlCla). This catalyst has been found to be especially effective and useful for the polymerization of propylene and butylene, but has little or no effect upon the polymerization of ethylene and owing to this fact the liquid products of polymerization in a catalytic gas polymerization operation `of this character tend to be deficient in lower boiling constituents orlight ends.

It is therefore an object of my invention to provide a gas polymerization processin which hydrocarbon gases containing gaseous oleflns may be polymerized to produce a low-boiling normally liquid product having a satisfactory balance or distribution between relatively low-boiling and relatively high-boiling constituents.

A further object of my invention is to provide an improved process for concentrating oleflnic gases, such as those produced in an oil-cracking operation prior and preparatory to the polymerization ofthe gases.

My invention has for further objects such additional improvements in operative advantages and results as may hereinafter be found to obtain.

My invention contemplates subjecting oleflnic gases, such as cracking-plant gases which have previously been subjected to fractionation to remove hydrogen and methane, to polymerization at moderately elevated temperatures and pressures in the presence of a catalyst comprising a sodium aluminum chloride, separating liquid products of polymerization from the unpolymerized gases and subjecting these gases to further polymerization under the influence of high temperature and pressure to effect a polymerization of such constituents, as for example, ethylene, which remain unpolymerized in the initial gas polymerization step, followed by separation of the liquid products of polymerization and blending 10 the liquid products of polymerization from both gas polymerization operations to form a balanced motor fuel.

My inventio'n further contemplates recycling residual gases remaining after both polymeriza- 15 tion operations, after fractionation to remove hydrogen and methane and also if desired after cracking to increase the oleflnic content thereof, to the initial or catalytic gas polymerization step. 20

My invention further contemplates, when cracking-plant gases are used as a source of olefins for polymerization, the fractionation of the cracking-plant gases by means of a liquefied butane fraction circulated through an absorber- 25 stripper cycle, the butane solvent being supplied from the stabilizing unit of the oil-cracking unit, and residual gases from the gas-fractionating unit being scrubbed with a suitable secondary solvent from the fractionating tower of the oil- 30 cracking unit to remove butane, together with the return of the butane-enriched secondary solvent -to the oil-cracking unit for recovery of the butane.

In order that my invention may be more clear- 35 ly set forth and understood, I now describe, with reference to the accompanying drawing forming a part of this specification, various preferred forms and manners in which my invention may be practiced and embodied. In this drawing, 40

Fig. 1 is a more or less diagrammatic elevational view of apparatus for carrying out the process of my invention in a preferred embodiment, the figure being intended to serve primarily as a flow diagram illustrative of my proc- 45 ess; and,

Fig. 2 is a similar view of an alternative form of a portion of the apparatus illustrated in Fig. 1.

Similar reference numerals designate similar 50 parts in both of the views of the drawing.

Referring now to the ligure, vapors from an oil-cracking unit which have previously been freed from heavy tarry or residual constituents enter the fractionator I from the cracking unit 55 through aline 2. 'Ihe fractionator I is provided with suitable cooling means, such as a cooling coil 3, and with conventional plates or Atrays 4 for assisting in the fractionation. As the vapors pass upward through the fractionator I they are partially condensed and fractionated to separate constituents heavier than gasoline, i. e., gas oil, which is removed from the fractionator I through a valved line 5. Overhead vapors from the frac' tionator I pass through a vapor line 6 to a condenser 1 and a separator 8, gasoline condensate being removed from the separator 8 through a line 9 having a valve I0 while the gases escape from the separator 8 through a. line I I.

The gases withdrawn from the separator 8 contain hydrogen, methane, higher paraiiins such as ethane, propane and butane and also gaseous ole'ns such as ethylene, propylene and butylene, the concentration of gaseous oleflns being dependent upon the conditions obtaining in the oil-cracking ysystem in which the gases have been produced. Before effecting the polymerization of the gases it is desirable to eliminate hydrogen and methane as far as possible.

For this purpose, the gases pass to a compressor I2 located in the line Il, Where they are compressed, for example to a pressure of from 100 to 300 pounds per square inch or more. The compressed gases are then cooled in a cooler I3, for example to a temperature in the neighborhood of 100 F., and the cooled compressed gases then enter a scrubber I4, which may be of conventional type, preferably internally provided with plates or ltrays or other gas-and-liquid contact devices I5. As the gases pass upward through the scrubber I4 they are subjected to countercurrent scrubbing by means of liquefied light hydrocarbons of the general boiling range of butane and/or pentane, and including corresponding olens, which is introduced into the scrubber I4 through a line I6 in suicient amount to effect an absorption of constituents heavier than methane. The scrubbed residual gases, comprising largely hydrogen and methane, but containing also some solvent, are removed from the scrubber I through a line I1 having a valve I8 and passed to a secondary scrubber I9, the purpose of which is to effect the re-absorption and recovery of any solvent contained in the gases leaving the scrubber I5.

In the preferred instance shown, the gases entering the secondary scrubber I9 are washed with a heavy naphtha fraction withdrawn from a Weir 20 in the fractionator I. This fraction passes from the Weir 20 through a line 2| having a valve 22 into the upper portion of the scrubber i9 and descends through the latter in counter-current to the rising gases, thus effecting a removal of butane and the like therefrom. Residual gases, comprising principally hydrogen and methane, are removed from the secondary scrubber I9 through a valved line 22', while the butane-enriched solvent is removed from the bottom of the scrubber I9 through a line 23 and delivered by means of a pump 24 located in the line 23 to the fractionator I.

The gasoline condensate removed from the separator 8 through the line 9 passes to a stabilizer 25 which is provided with a heating coil 26 located in the bottom thereof, cooling means such as a cooling coil 21 located in the upper undesired in the final gasoline product. Overhead vapors from the stabilizer- 25 pass through a line 30 and through the line II to the 'scrubber I5, while the stabilized gasoline is withdrawn from the bottom of the stabilizer 25 through a valved-line 3|. The operation of the stabilizer 25 is so conducted and the trap-out tray 28 is so located that a fraction comprising principally butane, pentane and corresponding oelfins is Withdrawn from the trap-out tray 29, and this fraction passes through a line 32 wherein is located a pump 33 into the line I6 and thence through a cooler 35 into the scrubber I5, where it serves to remove gaseous constituents having heavier molecular weights than methane from the gases entering the scrubber I5, as aforesaid.I

The enriched solvent reaching the bottom of the scrubber I5 is withdrawn through a line 36 having a valve 31 and passes to a stripper 39, which is internally provided with plates or trays 39 and with heating means such as heating coil 40 located in the bottom thereof. In the stripper 38 the enriched butane solvent is re-distilled and re-fractionated to drive off absorbed vapors and gases, the liberated vapors and gases passing through a line 4I to a condenser 42 and a sepa.- rator 43 from which a portion of the condensate is returned through a valved line 44 and a pump 45 to the upper portion of the stripper 38. The stripped butane fraction reaching the bottom of the stripper 38 passes by way of a line 46, wherein is located a pump 41, either through a branch line 48 having a valve 49 to the line I6 and thence into the scrubber I5, or through a branched conduit 50 having a valve 5I into the upper portion of the stabilizer 25. By regulating the valves 49 and 5I the proportions of the butane returned to the scrubber I4 and stabilizer 25 respectively may be varied as desired. For example, all of this stripped fraction may be returned to the stabilizer 25. Y The gases removed from the separator 43, which have been concentrated in oleiinic constituents by reason of the removal of hydrogen and methane therefrom, -pass by way of a line 52 having a valve 53 and a pump 54 into a heating coil 55 located in a furnace 56. Additonal olenic gases from an outside source (not shown) may also be introduced into the line 52 for delivery to the coil 55 by means of a line 51 having a valve 58. A portion of the condensate withdrawn from the separator 43 may also be delivered, by Way of a valved line 44', to the line 52 and thence to the coil 55, where it will be vaporized before passing to the reaction chamber 60.

The gases passing through the coil 55 are preferably heated to a temperature of from 300 to 400 F., under a pressure of from 500 to 1000 pounds per square inch, and at this temperature and under this pressure pass through a line 59 into a reaction zone or chamber 60 containing a supply of catalyst.

As catalysts for this purpose I prefer to employ metallic halides which have been treated to form complex molecular compounds by means of polary pared by fusing equi-molecular proportions of` anhydrous sodium chloride and aluminum chloride and is preferably suspended for use on an inert carrier such as pumice or other granular material. preferablydrom lto 20 mesh per inch in sise. It will be understood that while I have shown the catalyst as located in a reaction chamber 68 oi' more or less conventional type. contact between the catalyst and the gases may be obtained in any convenient manner and by means of any convenient apparatus which may be cooled i! desired to remove excess heat ofreaction.y Preferably the time of contact between the gases and the catalyst is of the order of 100 seconds but may vary from about 50 to 200 seconds, as desired.

The products then pass from lthe reaction chamber 60 through a line 6| to a fractionator 82, from which products heavier than gasoline are withdrawn through a valve line 62. and thence through a line 69 to a condenser 84 and a separator 65, from which unpolymerized gases are withdrawn through a line 68 having a valve 81. Liquid products of polymerization are withdrawn from the separator 65 through a line 68 having a valve 69 and pass to a conventional stabilizer 10, from which overhead gases return by way of a line 12 to the line 66 while stabilized motor fuel products pass through a valved line 13 into a receiver 14.

'I'he oleflnic gases passing through the line 66 which may if desired be supplemented with additional oleiinic gas from an outside source through a valved line 66' are compressed by means of a pump or compressor 15 to a high pressure, for example from 1000 to 3000 pounds or higher, and are then passed into a coil 16 located in a furnace 11, where they are heated to a polymerizing temperature of for example from 850 to 1200 F., and preferably from l000 to 1100VF., to initiate or effect polymerization oi' gaseous olefins. The products from the coil 16 may then pass either directly through a line 18 to a condenser 19, or may iirst pass through a reaction vessel 80. In any event, the time of contact is of the same order of magnitude as that employed in the catalytic gas-polymerization unit. From the condenser 19 the gases and condensate pass to a high-pressure separator 8|, where hydrogen and methane may be separated and removed through a valved line 82 while condensate passes through a line 83 having a pressure-reducing valve 84 into a low-pressure separator 85, which may be constructed as a conventional stabilizer if desired.

Gases withdrawn from the low-pressure separator or stabilizer 85, and comparatively rich in oleiinic constituents or paraillnic constituents heavier than methane as compared to the gases withdrawn at 82', pass by way of a line 86 having a valve 81 and a pump 88 to the line and thence into the scrubber I4. Condensate may pass through a valved line 90 to a receiver 9|, or, where insuiflcient stabilization has been effected at 85, may be delivered by means of a line |20 having a valve |2| and a pump |22 to the stabilizer 25.

When it is desired to increase the oleilnic constituents-.of the gases withdrawn from the separator 85, avalve 92 located in the line 86 may be closed and the gases from the separator 85 may pass through a line 93 having a valve 94 into a coil 95 locatedv Within a gas-cracking furnace 96. The gases passing through the coil 95 are heated to a gas-cracking temperature of for example from 1250 to l750 F. under a comparatively low pressure of from atmospheric to` 200 pounds per square inch and for a comparatively short period of time, for example from one or two seconds to 20 seconds in order to eifect a conversion of gaseous paralns to gaseous olefins. 'I'he cracked gases then pass by way of a line 91 having a valve 98 into a drum 99. Oil or oleilnic gases may be introduced through the transfer line 91 by means of a line |00 having a puinp |0| and a valve |02 for the purpose of quenching the hot gases. Oil, thus introduced in proper quantity. may be utilized as a source of further oleiinic gases. which are produced by the cracking of the oil introduced into chamber 99 under the influence of the hot gases.

Residual liquid products which may be formed during the cracking of the gases in the coil 95 or may comprise residual constituents of oil introduced through the line |00 are withdrawn from the drum 99 through a valved line |03 for disposition as desired. while gaseous and vaporousl products pass through a line |04 to a condenser |05 and then to a separator |06 where any'light condensate may be separated and withdrawn through a line |01. More elaborate fractionating means may of course be provided, especially where oil is introduced at |00. The cracked gases issuing from the separator |06 pass through a line |08 having a pump |09 and a valve I0 into the line 86 and are delivered into the scrubber' |4 for concentration.

As will be made clear from the discussion hereinabove, the products collected in the receiver 14 tend to be deficient in light constituents, while those collected in the receiver 9| tend to contain an excess of light constituents. 'I'he products collected in these receivers are therefore blended by delivering them in the quantities in which they are produced or in any other desired proportion into a blending tank III, valved lines I2 and I I3 being provided for this purpose. The blended motor-fuel product may then be withdrawn from the blending tank through a valved pipe 4 for use as desired or for further purification. If desired this product may be blended with stabilized gasoline drawn from the stabilizer 25 of the oil-cracking unit from which the gases supplied to the operation are derived.

If desired, a single gas separator may be employed in place of the highand low-pressure separators 8| and 85. 'Ihe gases from such a separator may pass either directly to the scrubber |5, or may rst pass to the coil 95 for cracking, or may be withdrawn from the system. When two separators 8| and 85 are used, the gases from the separator 8| may, if they contain enough parafflnic constituents heavier than methane to Warrant it, be delivered to the coil 95 for cracking to increase the oleiinic content thereof, the cracked gases returning to the scrubber I4.

In some instances, it may be desirable to employ the reaction vessel 60 as a gas reversion zone. crude or other heavy hydrocarbon oil may then be introduced under pressure into the vessel 60 from an outside source through a line having a pump 3| and a valve |32, to undergo cracking and/or reaction with gases in the presence of the catalyst. In this instance, the line 6| may be provided with a pressure-reducing valve |33 and the products from the vessel 60 pass into an evaporator |34, from which residual products are removed through a valved line |35, While vapors pass through a trap-out tray |36 into the fractionator 62.

As shown in Fig. 2, oil, such as reduced The condensate withdrawn at B2i maybe separately cracked to produce gasoline for blending with other products in the tank I I I.

This application is a division of my application Serial No. 750,857. filed October 31,1934', issued July 26, 1938 as Patent No. 2,125,235.

-While I have described my invention with respect to various specific examples and modifications by Way of il-lustrative examples and have illustrated various preferred forms of apparatus for carrying out the various operations incident to my process, it will be understood by those skilled in the art that my invention is not limited to such operative or mechanical details except insofar as set forth in the claims hereinafter made.

I claim:

1. The process of producing motor fuel from gases containing gaseous olens of from two to four carbon atoms per molecule, which comprises subjecting such gases to contact with a catalyst comprising a metallic halide combined with a polar compound at an elevated temperature and under high pressure to effect a polymerization of gaseous oleiins of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil containing motor fuel deficient in lower boiling constituents, recovering said oil, subjecting the remaining gases comprising ethylene as the main oleflnic,constituent and higher molecular weight paraiflns to a temperature above 1000 F. but not greater than 1200" F, and elevated pressure to effect conversion of said ethylene and said parailins to normally liquid lowboiling hydrocarbon oil containing motor fuel deficient in higher boiling constituents, recovering said oil and blending it with the first-mentioned low-boiling hydrocarbon oil to produce a motor fuel product.

2. 'I'he process of producing motor fuel from gases containing gaseous oleflns of from two to four carbon atoms per molecule, which comprises subjecting such gases to contact with a catalyst comprising a sodium aluminum chloride at a temperature of from 300 to 400 F. under a pressure of from 500 to 1000 pounds per square inch for a sufficient period of time to effect a polymerization of gaseous oleflns of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil containing motor fuel deficient in lower boiling constituents, recovering said oil, subjecting the remaining gases comprising ethylene as the main olenic constituent and higher molecule weight paraiiins to a temperature above 1000 F. but not greater than 1200 F. under a pressure in excess of 1000 pounds per square inch for a suiiicient period of time to effect conversion of said ethylene and said parafins to normally liquid low-boiling hydrocarbon oil containing motor fuel deiicient in higher boiling` constituents, recovering said oil and blending it with the iirstmentioned low-boiling hydrocarbon oil to produce a motor fuel product.

3. The process of producing motor fuel from gases containing gaseous olens of from two to four carbon atoms per molecule, which comprisesfractionating said gases to remove hydrogen and methane, subjecting the remaining gases to contact with a catalyst comprising a sodium aluminum chloride at an elevated temperature and under high pressure to effect a polymerization of gaseous oleflns of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil containing motor fuel deficient in lower boiling constituents, 'recovering said oil, subjecting the remaining gases comprising ethylene as the main olenic constituent and higher molecular weight paraflins to a temperautre above 1000i F. but not greater than 1200" F. and elevated pressure to effect conversion of said ethylene and said paraffins to normally liquid low-boiling hydrocarbon oil containing motor fuel de'cient in higher boiling constituents, separating said oil from residual gases and blending it with the ilrstmentioned low-boiling hydrocarbon oil to produce a motor fuel product, and returning residual gases thus obtained to the fractionating step. g

4. The process of producing motor fuel from gases containing gaseous oleflns of from two to four carbon atoms per molecule, which comprises fractionating said gases to remove hydrogen and methane, subjecting the remaining gases to contact with a catalyst comprising a sodium aluminum chloride at an elevated temperature and under high pressure to eiect a polymerization of gaseous olefins of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil containing motor fuel deficient in lower boiling constituents, recovering said oil, subjecting the remaining gases comprising ethylene as 4the main olefinic constituent and higher molecular Weight parafiins to a temperature above 1000 F. but not greater than 1200 F. and elevated pressure to effect conversion of said ethylene and said paraftlns to normally liquid low-boiling hydrocarbon oil containing motor fuel deficient in higher boiling constituents, separating said oil from residual gases and blending it with the firstmentioned low-boiling hydrocarbon oil to produce a motor fuel product, cracking residual gases thus obtained at a temperature of from 1250 to 1750 F. at relatively low pressure to increase their olefin content, and returning the thus cracked' of gaseous olens of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil containing motor fuel deficient in lower boiling constituents, recovering said oil, subjecting the remaining gases comprising ethylene as the main olenic constituent and higher molecular weight paraflns to a temperature above 1000 F. but not greater than 1200 F. and elevated pressure to effect conversion of said ethylene and said parains to normally liquid lowboiling hydrocarbon oil containing motor fuel deiicient in higher boiling constituents, separating said oil from residual gases and blending it with the first-mentioned low-boiling hydrocarbon oil to produce a motor fuel product, and returning residual gases thus obtained to the fractionating oil, the remaining gases substantially free of hydrogen and methane and comprising ethylene as substantially the only oleiinic constituent and higher molecular weight paramns through a heating zone and subjecting said gases therein to a temperature above l000 F. but not greater than 1200 F. and elevatedpressure to eil'ect a conversion of said ethylene and said paramns to normally liquid low-boiling hydrocarbon oil, and recovering said oil.

7. The process of producing motor fuel from gases containing gaseous oleilns of from two to four carbon atoms per molecule, which comprises subjecting such gas to contact with a catalyst under conditions of temperature and` pressure to eiiect a polymerization of gaseous oleilns of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil, recovering said oil, passing the remaining n gases substantially free of hydrogen and methane and comprising ethylene as substantially the only oleilnic constituent and higher molecular weight paramns through a heating sone and subjecting said gases therein to a temperature gs above 1000' F. but not greater than 1200 l".

and elevated pressure to eilect a conversion of said ethylene and said to normally liquid low-boiling hydrocarbon oil, recovering said oil and blending it with the first-mentioned low-boiling hydrocarbon oil to produce a motor fuel product.

8. The process of producing motor fuel from gases containing gaseous oleilns of from two to four carbon atoms per molecule, which comprises subjecting such gases to contact with a catalyst under conditions oi' temperature and pressure to eiTect a polymerization of gaseous oleilns of three and four carbon atoms per molecule to normally liquid low-boiling hydrocarbon oil, recovering said oil, passing the remaining gases substantially free of hydrogen and methane and comprising ethylene as substantially the only oleilnic constituent and higher molecular weight paramns through a heating zone and subjecting said gases therein to a temperature above 1000 l". but not greater than 1200' Il'. and elevated pressure to elect conversion of said ethylene and said paramns to normally liquid low-boiling hydrocarbon oil, separating said normally liquid low-boiling hydrocarbon oil from residual gases and returning residual gases thus obtained to said catalytic polymerization stage.

minou: v. A'rwm. 

